Metal frame for chairs with tubular elements

ABSTRACT

A metal frame for chairs with tubular elements, comprising two inverted U-shaped elements ( 10 ), which form the legs, two L-shaped elements ( 11 ), which form the support for the seat and the back and are each arranged next to one of the preceding elements, and two rod-like cross-members ( 12 ), which arc arranged in a lower region so as to join portions of the inverted U shaped elements and of the L-shaped elements. The cross-members ( 12 ) are joined to the other elements by projection welding at pairs of protrusions ( 13 ) determined by corresponding recesses ( 14 ) in the cross-section, obtained by means of a flattening plastic deformation.

TECHNICAL FIELD

[0001] The present invention relates to a metal frame for chairs withtubular elements.

BACKGROUND ART

[0002] Metal frames for chairs with tubular elements are already knownwhich comprise two elements shaped like an inverted U, which form thelegs, two L-shaped elements, which form the support for the seat and theback and are each arranged next to one of the preceding elements, andtwo rod-like cross-members, which are arranged in a lower region so asto join portions of the inverted U-shaped elements and of the L-shapedelements.

[0003] These elements are currently assembled and joined one another byresting the cross-members against the inverted U-shaped elements and theL-shaped elements, whose cross-section is normally substantiallyellipsoidal, and by then performing gas welding with deposition of weldmaterial, for example electric continuous-wire welding.

[0004] The problem currently found in this type of structure is indeedcaused by the type of welding, which requires long execution times andthe consumption of material related to the wire and to the gas.

[0005] This, in terms of cost containment, is currently an importantaspect, since chairs using the above described structure are ratherwidespread commercially and are manufactured by several companies, andtherefore their costs are highly influenced by the presence ofcompetition.

DISCLOSURE OF THE INVENTION

[0006] The aim of the present invention is to provide a metal frame forchairs with metal tubular elements that eliminates the drawback notedabove in known types.

[0007] Within this aim, a consequent primary object is to shortenproduction times and reduce the associated costs.

[0008] Another object is to provide a frame that is at least as solid asthat of currently commercially available frames.

[0009] Another object is to provide a frame that can be manufacturedwith per se known technologies.

[0010] This aim and these and other objects that will become betterapparent hereinafter are achieved by a metal frame for chairs withtubular elements, of the type comprising two inverted U-shaped elements,which form the legs, two L-shaped elements, which form the support forthe seat and the back and are each arranged next to one of the precedingelements, two rod-like cross-members, which are arranged in a lowerregion so as to join portions of the inverted U-shaped elements and ofthe L-shaped elements, characterized in that said cross-members arejoined to the other elements by projection welding at pairs ofprotrusions determined by corresponding recesses in the cross-section,obtained by means of a flattening plastic deformation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Further characteristics and advantages of the invention willbecome better apparent from the following detailed description of anembodiment thereof, illustrated only by way of non-limitative example inthe accompanying drawings, wherein:

[0012]FIG. 1 is a bottom perspective view of a frame having thestructure according to the invention;

[0013]FIG. 2 is an enlarged-scale perspective view of a detail of theframe of FIG. 1;

[0014]FIG. 3 is an enlarged-scale side view of the frame of FIG. 1;

[0015]FIG. 4 is another enlarged-scale perspective view of a detail ofthe frame of FIG. 1;

[0016]FIG. 5 is a sectional view of the detail of FIG. 4;

[0017]FIG. 6 is a perspective sectional view of a portion of the framedeformed by flattening;

[0018]FIG. 7 is a view of another detail of FIG. 4.

WAYS OF CARRYING OUT THE INVENTION

[0019] With reference to the figures, a metal frame for a chair withtubular elements comprises two inverted U-shaped elements 10, which formthe legs, two L-shaped elements 11, which form the resting support forthe seat and the back, not shown in the figures for the sake ofsimplicity, each arranged next to one of the preceding elements 10, andtwo rod-like cross-members 12 arranged in a lower region so as to jointhe inverted U-shaped elements 10 and the L-shaped elements 11.

[0020] The elements 10 and 11 are made of metal tube, with across-section that is substantially elliptical but can also be oval,while the cross-members 12 are straight and have a circularcross-section.

[0021] According to the invention, the cross-members 12 are joined tothe inverted U-shaped elements 10 and to the L-shaped elements 11 byprojection welding at pairs of protrusions 13 formed by correspondingrecesses 14 in the cross-section, produced by a flattening plasticdeformation.

[0022] In practice, as regards the inverted U-shaped elements 10,welding is performed proximate to the bending regions, extending therecesses that are provided in the regions that are not visible in orderto form the bend, which as is known would otherwise produce wrinkle dueto the excess of material in the regions having a smaller radius.

[0023] As regards the L-shaped elements 11, instead, at the front theflattening must be provided expressly, since a region not adjacent tobends is to be welded, while at the rear the flattened portion of thebend 15 is used (an extension of the flattened portion of the rear bendup to the front region can also be provided).

[0024] From the point of view of manufacture, it is simply necessary toprovide an extension of the punches that produce the flattened regionfor the bend 15 and to provide new punches for the front regions of theL-shaped elements 11.

[0025] In the end a frame is obtained in which welding is performedwithout depositing material, simply and rapidly, since the welding spotsare determined directly by means of the plastic deformation operation,which is required, both for the elements 10 and for the elements 11, dueto the need to bend the components.

[0026] Furthermore, projection welding is a quick operation, which isperformed simultaneously for a plurality of regions, without having toproceed in succession, portion by portion, as currently entailed by wirewelding.

[0027] In practice it has been observed that the intended aim andobjects of the present invention have been achieved.

[0028] In practice, the materials employed, so long as they arecompatible with the contingent use, as well as the dimensions, may beany according to requirements.

[0029] The disclosures in Italian Utility Model Application No.PD2001U000001 from which this application claims priority areincorporated herein by reference.

1. A metal frame for chairs with tubular elements, of the type comprising two inverted U-shaped elements (10), which form the legs, two L-shaped elements (11), which form the support for the seat and the back and are each arranged next to one of the preceding elements, two rod-like cross-members (12), which are arranged in a lower region so as to join the inverted U-shaped elements and the L-shaped elements, characterized in that said cross-members are joined to said U-shaped elements and said L-shaped elements by projection welding at pairs of protrusions (13) determined by corresponding recesses (14) in the cross-section, obtained by means of a flattening plastic deformation.
 2. The frame according to claim 1, characterized in that said inverted U-shaped elements (10) and said L-shaped elements (11) are made of metal tube having a substantially oval or elliptical cross-section, while said cross-members (12) are straight and have a circular cross-section.
 3. The frame according to claim 1, characterized in that for said inverted U-shaped elements (10), welding is performed proximate to bends (15), extending the recesses that are provided in the regions not in view in order to produce the bend.
 4. The frame according to claim 1, characterized in that for said L-shaped elements (11) the flattened portion is, at the front, in a region that is not adjacent to bends and is provided, at the rear, proximate to the bends, extending the recesses that are provided in order to produce the bend. 